Lehman made rifles to fulfill the orders of customers over a fairly long period of time. This was a gun manufactory, not a little shop. They made what the customers ordered, several styles at a time if there were orders from different customers each wanting their own specifications. Styles were changing fast and the end users were varied. So it's not simply a case of saying, "Lehman's rifles were mostly caplocks" or "mostly flintlocks" or "mostly fullstocks", or "mostly halfstocks" etc. To exaggerate, that would be kind of like saying, "Remington shotguns are mostly 12 gauge pumps" or "Winchester rifles are mostly 30-30 lever actions."
In general, whomever is trying to sell you a Lehman (or Leman) is going to try to tell you that their model is THE accurate one.
Leman's are late period guns, most of them made after the percussion system was well established, most well after the mountain men had caught their last beaver. There are plenty of other trade guns that were more plentiful and better characterized. Henry probably sold more trade guns than all the rest combined. The Trade Gun Sketch Book is a very cheap resource that has full-sized drawings of the more common trade guns used in the West.
Wheeler Trade Rifle- 1790-1820, .53 caliber fullstock, British made, flintlock of course in this period. Simple cast brass patchbox, all brass mounts- a heavy longrifle, 45" barrel. Rounded cheekpiece.
Henry Lancaster pattern 1822-1855- all brass mounts, brass patchbox, 42-44" barrel, .47-.55 caliber, fullstock, flint until 1840, then percussion.
Henry English Pattern- 1825-1855, same patchbox as the Wheeler, round cheekpiece, flinter-42-44" barrel, .53 caliber- looks like a gun made to please those used to Wheeler rifles.
Henry Scroll guard- 1834-1855 (New English Pattern) different trigger guard, that's the main difference.
Derringer flint Indian rifle- 1809-1837. Brass mounted, 4 piece patchbox, longrifle, flintlock, 45" barrel, .50-.53 caliber.
Tryon Indian Rifle- short barreled, 35" but 1 and 3/16 across the flats, 10.5 pounds, .52-.54, nice brass 4 piece patchbox, engraved, flintlock, fullstock.
"Leman Indian Rifle 1850-1870"- brass or iron buttplate, brass patchbox (capbox, really), percussion, drum and nipple, short barrel 31", 1 and 1/16" across flats, fullstock, Tennessee style cheekpiece.
Henry and son halfstock, 1856-1870- brass mounted, scroll guard, patent breech, double set triggers, cast brass patch/capbox. 34" barrel, 1 and 1/8" across flats, .50. Cast brass forend tip. 9.5 pounds. "sturdy gun much like a Hawken at half the price".